Cucurbitacin B, which was isolated from the fruit juice of Trichosanthes cucumerina, possessed strongly cytotoxic action against KB cell (human nasopharynx carcinoma cell) (Silapaarcha et al, 1981) and human breast cancer cells (SKBR3 (ER-), MCF7 (ER+) and MDA-MB435 (ER-)) (Jiratchariyakul et al, 1992;Jiratchariyakul et al, 1999;Kongtun et al, 2009).The mechanism that cucurbitacin B inhibited the breast cancer cells could be explained by arresting the cell cycle at G2/M phase and inducing the apoptosis.Cucurbitacin B inhibited tolemerase activity leading to the triggering of cell cycle arrest.The decrease of hTERT (human telomerase reverse transcriptase) and the pro-oncogenic genes (c-Myc) in the treated breast cancer cells was expressed (Duangmano et al, 2010).Cucurbitacin B also interrupted the Wnt signaling and induced the apoptosis.The decreased expression of Wnt-associated signaling molecules (β-catenin, galectin-3, cyclin D1 and c-Myc) was observed (Dakeng et al, 2012).